Chunk_ID not working in the S3 output config

[hackerx15]

Describe the bug

Once we started using chunk_id in our s3_object_key_format, fluentd started giving the following output in the config
2021-04-13 14:01:03.217825851 +0000 fluent.warn: {"message":"chunk key placeholder 'chunk_id' not replaced. template:${$.logging_path}/%Y/%m/%d/%{time_slice}_${chunk_id}.gz"}

To Reproduce

The config used for S3 with the output config mentioned below does the job of reproducing the error.

Expected behaviour

Unique chuck id being created for s3 log files

Your Environment

• Fluentd version: fluentd 1.12.2
• Operating system: NAME="Alpine Linux" ID=alpine VERSION_ID=3.12.5 PRETTY_NAME="Alpine Linux v3.12" HOME_URL="https://alpinelinux.org/" BUG_REPORT_URL="https://bugs.alpinelinux.org/"
• Kernel version: 4.14.225-169.362.amzn2.x86_64

Your Configuration

      output: |-
        <match **>
          @type copy        
          <store>
            @type s3
            s3_bucket "logging-#{ENV['CLUSTER_ENV']}"
            s3_region "#{ENV['AWS_REGION']}"
            path ${$.logging_path}/%Y/%m/%d/
            s3_object_key_format %{path}%{time_slice}_${chunk_id}.%{file_extension}
            store_as gzip_command
            <buffer time,$.CLOG.long_path>
              @type file
              path /fluentd/log/s3
              timekey 600
              timekey_wait 60
              timekey_use_utc true
              chunk_limit_size 256MB
              total_limit_size 48GB
              flush_at_shutdown true
              overflow_action block
              retry_forever true
              retry_type periodic
            </buffer>
            <format>
              @type json
            </format>
          </store>

Your Error Log

2021-04-12 16:08:47 +0000 [warn]: #0 failed to flush the buffer. retry_time=441 next_retry_seconds=2021-04-12 16:08:48 +0000 chunk="5bfc89a5262fb7daf14f2919e78de036" error_class=RuntimeError error="duplicated path is generated. use %{index} in s3_object_key_format: path = loadtester/sbx/system/2021/04/12/202104121550_.gz"

Additional context

s3_object_key_format %{path}%{time_slice}_%{hex_random}.%{file_extension} hex_random config instead of chunk_id works without any issue.

[fujimotos]

@hackerx15 I fixed your issue in #3339.